Alternating-current dynamo-electric machine



(No Modl.)

Patented Feb. 12, 1895.

the objections incident to UNITE STATES PATENT Orrrcs AXEL EKSTROM, OF LYNN, ASS IGNOR TO THE GENERAL ELECTRIC COM- PANY, OF BOSTON, MASSACHUSETTS.

ALTERNATlNG-CURRENT DYNAMO-ELECTRlC MACHINE.

SPECIFICATION forming part of Letters Patent No. 533,873, dated February 12, 1895.

Application filed July 26, 1894; Serial No. 518,661. (No model.)

To all whom it may concern.-

Be it known that I, AXEL EKSTROM, a citizen of the United States, residing at Lynn, in the county of Essex, State of Massachusetts, have invented certain new and useful Improvements in Alternating-Current D ynamo- Electric Machines, of which the following is a specification.

My invention relates to alternating current dynamo-electric machines; and has for its object to provide a means of compounding such machines which shall obviate some of present arrangements.

It is well known that in the construction of alternators a portion of the current of the machine must be passed through a commu tator and thence around the field-magnets, in order to compound them for the proper rise of potential under increase of load. This operation, simple in principle, is difficult in practice, because, where the entire current is commuted, the sparking at the commutator is so great as to destroy its surface, and the number of segments of the commutator being necessarily small, the act of commutation has to deal in each case with very large current. It has been the practice to put a shunt around the commutatorof such resistance as to force through the commutator just the proportion of exciting current deemed desirable by the designer; but in practice it is objectionable to make this shunt of sufficient size to take the amount of current required to save the commutator contacts.

It is to obviate these difficulties that I have devised my invention, which consists in adding to the present arrangement a second auxiliary shunt of considerable capacityinserted between one terminal of the armature windings, the collecting ring and the commutator, in the manner hereinafter described, by which the larger portion of the current is carried direct to the collecting ring without passing through the commutator or the outside shuntl This shunt I prefer to arrange upon the armature itself, and thus avoid sliding connections of any kind.

The accompanying drawing shows a diagrammatic representation of my invention.

A is the armature, of which 13, B are the coils.

O is the field-magnet system, D being the windings thereon. I have illustrated only the series winding upon the coil, but it is to be understood that the usual separate exciter is employed so as to provide the machine with the compound field necessary.

E, E are the collecting rings, of which e, e are the brushes F is the commutator provided with the brushes fif, and G is the outside shunt commonly employed,

g, h,t' are the leads to the armature coils and interior shunt respectively.

a]; are the mains.

0, cl are the terminals of the armature coils.

H is the revolving shunt carried by the armature.

The construction and operation of the machine will be readily understood from the foregoing description.

The coils of the armature, as illustrated in the drawing, are in multiple. From the terminal d the lead 11 goes to the collecting ring E, the current passing over the line b. The path from the terminal 01 through the armature coils is in multiple to the other terminal 0 from which point it has two paths provided, one by the lead g direct to the commutator, the other through the shunt H and by the lead 72. to the collecting ring E. The current passing in the commutatoraud through the shunt G goes around the field-magnet coils from the brush f, for instance, and thence returns to the brush fand by the lead h from the commutator to the collecting ring E and the line Ct.

As thus illustrated and described, I provide a path for part of the current which avoids the commutator altogether; and the resist- .ances of the two shunts G and H are so proportioned that just the amount of current desired will pass through the commutator and around the field magnet coils. It is manifest that this current will also depend upon the amount of current in the main circuit and that thus the compounding action, as ordinarily performed in alternators, willbe efficient and complete.

What I claim as new, and desire to secure by Letters Patent of the United States, is

1. In an alternating current dynamo-electrio machine, the combination of a revolving armature with coils adapted to generate an alternating current, and a shunt between one terminal of such coils and one of the collecting rings, the shunt carried by and revolving with the armature, as herein described and set out.

2. In an alternating current dynamo-electric machine, and in combination, coils carried upon a revolving armature, one terminal of such coils connected to collecting rings and. the other terminal to a commutator, and a shunt between one of the terminals, the coleeaere hand this 21st day of July, 189 i.

AXEL EKSTROM.

Witnesses:

JOHN W. GIBBONEY, HENRY O. WEs'rENDARP. 

